The long-term objective of this project is to understand spoken language processing (particularly speech perception and auditory word recognition) in linguistic context. Speech signals are unique in human experience because they are highly familiar, and have great practical significance in daily life. Therefore, it is not too surprising to find that people develop optimized processing strategies tuned specifically for speech (cf. Werker & Tees, 1984; Kuhl et al., 1992). In this project, we study how this tuning process may be sensitive to linguistic structure. Two key questions are addressed in the proposed work. (1) What in the speech perception mechanism is altered by linguistic experience? and (2) how is linguistic/phonetic information encoded for speech processing? These questions will be addressed in a set of nine studies that address four specific aims. (1) Distinguish between language-specific perceptual processing and language-universal auditory sensitivity for speech sounds. (2) Determine whether language-specific speech processing is tied to the lexicon. (3) Test the claim that phonetic/perceptual knowledge is oriented toward handling distinctive phonological features. (4) Model the experimental results in an explicit theory of speech perception.